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DIY brushing glazes by-the-jar:

Here is my setup to make them

Let's make a DIY low SG version of G2934BL. Weigh out 340g of dipping glaze powder. Include 5g Veegum (to gel the slurry to enable more than normal water) and 5g CMC gum (for slow drying and brushing properties). Shake-mix all the powder in a plastic bag. Pour it into 440g water, blender mix on low speed, then finish with 20 seconds on high speed. This fills a 500ml jar. In subsequent batches, I adjust the Veegum for more or less gel, the CMC for slower or faster drying and the water amount for thicker or thinner painted layers. Dipping glaze recipes can and do respond differently to the gums. Those having little clay content work well (e.g. reactive and crystalline glazes). If bentonite is present, it is often best to leave it out. Recipes having high percentages of ball clay or kaolin might work best with less Veegum. Keep good notes (with pictures) to reach the objective of good brushing properties. Use code-numbering on the jars and test pieces.

Here is some incentive: Brushing glazes have gotten to the point where it can cost $5 to glaze one mug! This is so worthwhile doing that I make custom labels for each jar!

Related Pictures

Dipping glazes has one big advantage over brushing them

They go on evenly, in one coat, and dry in seconds.

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Commercial brushing glazes are laced with CMC gum to make them paint on thin and dry slowly. Why would anyone want that? Layering. Brushing requires multiple layers, so it is difficult to get even coverage! And it takes lots of time. What if you want it to go on thick enough at one go, dry in seconds and apply evenly. DIY potters have that ability by making thixotropic dipping glazes. You cannot buy these because the gum kills thixotropy at the specific gravities potters use. Thixotropic glazes are fluid in the bucket but gel after a few seconds of standing. This enables really good dipping properties - the gelling enables the glaze to stay in place upon extraction from the bucket. This picture demonstrates how such glazes hang on to even non-absorbent and wet surfaces.

Bottom: Extreme thixotropy. The spatula is held vertical by gelling only (a pure EPK slurry). Yet when this slurry is put in motion, it is fluid!
Top left and right: These spatulas were slowly extracted and the engobe and glaze just hang on in a perfectly even layer. On a bisque surface, the glaze dries quickly, within seconds. And the engobe hangs on to leather hard ware for perfect coverage, even around sharp contours.

Prepare your own glazes for three application methods

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Potters commonly mix glazes from recipes, while hobbyists often use bottled commercial products intended for brushing. But the same glaze powder batch can be prepared in quite different ways depending on how it needs to be applied.

• Dipping glazes need a slurry that is sufficiently thixotropic (to suspend well, apply evenly, stop flowing after withdrawal). They dry quickly on porous bisque. They normally contain little or no gum, so the dried layer does not need to be especially hard. Industrial versions are high-solids, pottery versions are usually low-solids.
• Brushing glazes need to behave more like paint. CMC gum slows drying, improves brushing and levelling, and hardens the dried layer so it adheres well and can tolerate multiple coats. Commercial versions are generally low-solids, while potters have the liberty to mix as high-solids.
• Base-coat dipping glazes are a compromise between the two. They must still gel, drain and dry quickly enough for dipping, but they also need enough gum and dry strength that another glaze can be applied over them without the first layer softening, lifting or letting go of the body.

Here’s how I make a base brushing engobe




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This brushing engobe has already passed my EBCT test for use on the intended body. It is thick and gooey (because it contains CMC gum), so it is practically impossible to sieve. My regular propeller mixer is not able to break up the tiny agglomerates of New Zealand kaolin. But 30 seconds of blender mixing makes it as smooth as silk. To make this liter of brushing engobe, I use 800g of powder and 10g of CMC gum in 800g of water. Because of the very high clay content, this does not require Veegum to gel it. The CMC gum greatly improves the brushing properties. It also thins the slurry enough to enable its lower-than-normal water content, making it more suitable for painting onto leather-hard ware, often in as little as one coat.

Two methods to make your own low SG brushing glaze.




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Dipping glaze applies and dries in seconds. Brushing glazes dry slowly and dry hard. Brushing glazes simply have gum in the recipe, dipping glazes typically do not. This is the Alberta Slip cone 6 base, made jet black with 4% black ceramic stain (our code G3914A). We normally mix this as a dipping glaze but I have made a 500ml jar of low SG brushing version using both of the following methods. These methods will work for almost any glaze recipe (for those having exceptionally high clay content less Veegum is needed).

1) Shake together, in a plastic bag, 340g of mixed glaze powder with 5g of Veegum and 5g of CMC gum. Add that to 440g of water in a kitchen blender and mix on high speed until it gels (the gums resist mixing so the highest speed for at least 30 seconds is needed to prevent lumps).

2) Take 680g of dipping glaze (assuming it is about 50:50 water:powder you get 340g of dry), put that in the blender with another 80g of water and proceed as in method 1. Less total water is being used because the dipping glaze might not be exactly 50:50 water:powder. During mixing, if it gels too much add the extra 20g of water.

Control gel using Veegum, brushing properties with CMC gum




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This is G1214Z1 brushing glaze (with 5% titanium added). For a 340g powder batch (to get a pint) my initial target is 5g CMC gum and 5g Veegum. CMC controls drying speed and Veegum the amount of gelling. I first mix the CMC with the powder and shake the whole batch in a plastic bag. Then I add it all to 440g of water in the blender jar and mix it well (making sure no agglomerates remain (stage 1). Stage 2 is adding the VeeGum slowly, while high-speed blender-mixing, this is important because it enables tuning the degree of gel (which cannot be predicted). Because this recipe has little clay, it took all 5g of Veegum without overgelling (the entire mass moved freely in the mixer jar). But it did gel overnight (so 4g would be better next time). By contrast, it is the brushing behavior that demonstrates whether the amount of CMC is right. Not enough and coats dry too fast and go on too thick. Too much and it dries too slowly and too many coats are needed.

Glaze bowls by brushing instead of dipping:

Convert your dipping glazes to brushing




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This wheel-thrown bowl is heavy and thick-walled. Applying dipping glazes, both the outside and inside, can be cumbersome, slow and trouble prone (especially where two difference colors must meet at the rim). It turns out that the hobbyist way of brushing glazes can actually better for this. I make these 500ml jars of brushing glaze and tune the percentage of gums to get the right painting consistency and drying time. Applying multiple coats by brush takes only a few minutes, and no wax resist or any other tools are needed. And it is easy to meet two glazes in a straight line at the rim. On this piece, the inside glaze is G2936B and the outside is G2926B. Both are almost always used as thixotropic dipping glazes for other types of ware, but nothing about their recipes disqualifies them from being mixed as brushing glazes.

Brushing glazes on large bowls:

Pour-feed the brush in one long stroke




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On the left I applied pure Ravenscrag slip, as a glaze, inside and out, using only a small brush. I did the same to the bowl on the right, using the G1947U transparent glaze. Both of H550 clay. We almost always use these as dipping glazes. But here I mix them as brushing glazes, adding 10g CMC gum powder to one liter of a water-reduced version of the slurries. Blender mixing makes it possible to mix in the powdered gum and tune water content for the best brushing experience. The gum slows down the drying speed dramatically so there is plenty of time to brush it into place (while the wheel is turning). The gum also greatly increases the cohesion, enabling pouring out of a pitcher in a long thin stream. In this firing I also glazed a leather hard 40-inch tall vase and a 35 lb bone-dry bowl using the same technique. The evenness of coverage was the best I have ever gotten (of any technique) on large sizes and shapes.

It might surprise you that handmade tile is often glazed using brushing. A glaze can be squirted onto a tile and spread with a large brush in seconds. This can be done on a passing conveyor or in batches on a table.

Links

Glossary	Blender Mixing An ordinary kitchen blender does a better job of mixing a ceramic slurry than any industrial machine. It even reduces clay particle size and hyper ages it.
Glossary	Brushing Glaze Hobbyists and increasing numbers of potters use commercial paint-on glazes. It's convenient, there are lots of visual effects. There are also issues compared to dipping glazes. You can also make your own.
Materials	CMC Gum CMC gum is indispensable for many types of ceramic glazes. It is a glue and is mainly used to slow drying and improve adhesion and dry hardness.
Articles	Where do I start in understanding glazes? Break your addiction to online recipes that don't work or bottled expensive glazes that you could DIY. Learn why glazes fire as they do. Why each material is used. How to create perfect dipping and brushing properties. Even some chemistry.

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